London Underground

The London Underground, also known as The Tube, is a public rapid transit system serving London, England and parts of Buckinghamshire, Essex, and Hertfordshire. It originated as the Metropolitan Railway, the world's first underground passenger railway, opened in January 1863. In 1890, the opening of the City & South London Railway marked the first line to operate underground electric traction trains. The Travelcard ticket was introduced in 1983 and the Oyster card in 2003, and, from 2017 to 2018, the Underground carried 1.357 billion passengers, making it the 12th-busiest metro system in the world.